LibJS: Clarify Object (base class) construction somewhat

Divide the Object constructor into three variants:

- The regular one (takes an Object& prototype)
- One for use by GlobalObject
- One for use by objects without a prototype (e.g ObjectPrototype)

Libraries/LibJS/Runtime/JSONObject.cpp

@@ -38,7 +38,7 @@
 namespace JS {
 
 JSONObject::JSONObject(GlobalObject& global_object)
-    : Object(global_object.object_prototype())
+    : Object(*global_object.object_prototype())
 {
 }